1. Field of the Invention
This invention relates to fluid handling processes and apparatus. More particularly, this invention relates to a fluidic oscillator that can operate at the colder temperatures usually associated with higher viscosity fluids.
2. Description of the Related Art
Fluidic oscillators are well known in the prior art for their ability to provide a wide range of liquid spray patterns by cyclically deflecting a liquid jet. The operation of most fluidic oscillators is characterized by the cyclic deflection of a fluid jet without the use of mechanical moving parts. Consequently, an advantage of fluidic oscillators is that they are not subject to the wear and tear which adversely affects the reliability and operation of other spray devices.
Examples of fluidic oscillators may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer), U.S. Pat. No. 6,186,409 (Srinath) and U.S. Pat. No. 6,253,782 (Raghu).
A simplification of the nature of the typical oscillations in the flow of a liquid exhausting from such devices into a gaseous environment is shown in FIGS. 1A-1C. For this assumed two-dimensional flow, the alternating formation of vortices in the oscillator's interaction chamber is seen to cause the flow from its outlet at a particular instant to be alternately swept downward (FIG. 1A) or upward (FIG. 1B) such the oscillator's output is spread over a fan angle of approximately 2θ (FIG. 1C).
This type of oscillating liquid jet can yield a variety of patterns for the downstream distribution of the liquid droplets that are formed as this liquid jet breaks apart in the surrounding gaseous environment. One such possible distribution pattern is shown in FIG. 1C.
For the spraying of some high viscosity liquids (i.e., 15-20 centipoise), the “mushroom oscillator” disclosed in U.S. Pat. No. 6,253,782 and shown in FIG. 2 has been found to be especially useful. However, it also has been found that, as the temperature of such liquids continues to decrease so as to cause their viscosity to increase (e.g., 25 centipoise), the performance of this type of oscillator can deteriorate to the point where it no longer provides a jet that is sufficiently oscillatory in nature to allow its spray to be distributed over an appreciable fan angle. This situation is especially problematic in windshield washer applications that utilize such fluidic oscillators.
Despite much prior art relating to fluidic oscillators, there still exists a need for further technological improvements in the design of fluidic oscillators for use in colder environments.
3. Objects and Advantages
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide new, improved fluidic oscillators and fluid flow methods that are capable of generating oscillating, fluid jets with spatially uniform droplet distributions over a wide range of operating temperatures.
It is another object of the present invention to provide improved fluidic oscillators and fluid flow methods that are capable of generating oscillating, fluid jets with high viscosity liquids.
It is yet another object of the present invention to provide improved fluidic oscillators and fluid flow methods that yield fluid jets and sprays of droplets having properties that make them more efficient for surface cleaning applications.
These and other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying summary, drawings and the detailed description that follows.